A residential water and hot-water supply piping system usually adopts a header method, in which a water supply main pipe and a hot-water supply main pipe are connected respectively to a metallic water supply header and a metallic hot-water supply header, and the respective headers branch into multiple water supply branch pipes and multiple hot-water supply branch pipes that are connected to connection portions of facilities and equipment.
In header piping systems adopting such a header method, a main pipe installed in a residential underfloor space is connected first to the body of a header and then to branch pipes of the header through multiple branch connection portions, and the branch pipes run through the underfloor space and are connected to connection portions of facilities and equipment.
To connect a main pipe and branch pipes respectively to a header body and branch connection portions, such header piping systems may adopt, for example in view of easy replaceability of the main pipe and the branch pipes, a connection method in which pipe joints connected to either a main pipe or branch pipes are screwed into a header body or branch connection portions.
On the other hand, headers made of synthetic resins are used in recent years. In cases where pipe joints are coupled to pipes by screws, synthetic resin headers have strength disadvantages because large forces act on screwed portions. Thus, in cases of using synthetic resin headers, a method known as fastener connection is adopted as described in Patent Document 1, the method using elastic splicing fittings to connect a header body and a pipe joint and to connect branch connection portions and pipe joints, with flanges butting against one another.
If headers are made of synthetic resins, the branch connection portions may possibly be expanded due to internal water pressures. With this in view, Patent Document 2 proposes a technique for coupling branch connection portions to plugs provided with a spread preventing portion that prevents a branch connection portion from being expanded due to internal water pressures.
Patent Document 1: JP2005-188682A
Patent Document 2: Japanese Patent No. 3578696